Indeed. I've had delicious brews and shots from roasts as low as 12% and also as high as 30%. 20-25 is a good range for a typical washed coffee, but there are many outliers out there.

I think it is very important to consider the overall roast time when figuring DTR. In my experience faster/hotter roasts develop much faster and require a shorter DTR. If my final time was under say 11min. my DTR would probably be less than 20%. Also if the ROR is not perfectly steadily declining "which I have a hard time with" then the 20-25% is also out the window. If the ROR significantly drops or rises then the development will be stalled or rushed and Scott's recommendations will no longer apply.

Hi all,

I've learned through writing books that 90 pages of words is often distilled to a few soundbites. When I wrote the book, the idea of development-time ratio and an always-declining ROR were novel concepts. Unfortunately, though "20%--25% DTR" works well for most people roasting at 60%-90% capacity to a medium (not Nordic, not second crack) roast level, with a reasonably steady ROR line, I find that the professionals who given an "eye roll" when my name is mentioned don't really think about the 20%-25% in context.

In one of the Cat & Cloud podcasts, Deaton distilled my ideas to soundbite and then proposed a roasting method that would guarantee baked coffee; as many do, he ignored all context, as well as the value of a steadily-declining ROR. The blog post, which I hope most of you will read, is meant to clarify that context.

Personally, I think it's fine if roasters use a 15% DTR; what matters to me is that their ROR is steadily declining and their coffee is well developed, whatever the roast level. And I were roasting a 40%-capacity batch in a roasting competition, a low DTR would be reasonable, but it wouldn't be if I were to roast a full batch in that same machine. But if one tries to roast, say, a >80% capacity batch in a Probat to a medium roast, 15% DTR would probably not be too successful (to my palate.)

Given that I was writing a book that would (hopefully) be read by all sorts of roasters (pros, home roasters, light roasters, dark roasters, really dark roasters, roasters with ROR curves that look like the path of a drunk driver...) I wanted to recommend a DTR range that would apply to 80%--90% of the world's coffee. From what I've seen in my travels, those of us who drop roasts just after FC ends, or similar times, are in the small minority. More than 90% of the world's coffee seems to still be roasted to, or into, second crack. I didn't want to help improve 10% of the world's roasting; I wanted to help improve 90% of it. Countless roasters, from tiny 3rd-wave-Nordic types to giant, dark commercial types, have emailed me to thank me for helping them improve their coffee dramatically. Nothing will work for everyone, and nothing will please everyone. But I did my best.

Part of the inspiration behind the new blog is to discuss roasting ideas with more context and nuance than would have been feasible in the book. And hopefully one day I'll hear people discuss my ideas without thinking simply that Rao = 20%--25% DTR.

thanks
Scott Rao
www.scottrao.com/blog

Thanks Scott for clarifying your intended audience!

While we are discussing how Mr Rao's name is taken in vain, what is the "Rao Spin"???

Unrooted wrote:While we are discussing how Mr Rao's name is taken in vain, what is the "Rao Spin"???

Start at about 1:20 in on the video below.

Thanks for writing your book..
It was nice to get one persons opinion from start to finish...

bigabeano wrote:Given that I was writing a book that would (hopefully) be read by all sorts of roasters (pros, home roasters, light roasters, dark roasters, really dark roasters, roasters with ROR curves that look like the path of a drunk driver...) I wanted to recommend a DTR range that would apply to 80%--90% of the world's coffee. From what I've seen in my travels, those of us who drop roasts just after FC ends, or similar times, are in the small minority. More than 90% of the world's coffee seems to still be roasted to, or into, second crack. I didn't want to help improve 10% of the world's roasting; I wanted to help improve 90% of it. Countless roasters, from tiny 3rd-wave-Nordic types to giant, dark commercial types, have emailed me to thank me for helping them improve their coffee dramatically. Nothing will work for everyone, and nothing will please everyone. But I did my best.

Part of the inspiration behind the new blog is to discuss roasting ideas with more context and nuance than would have been feasible in the book. And hopefully one day I'll hear people discuss my ideas without thinking simply that Rao = 20%--25% DTR.

I use a fluid bed machine and drum roasting finesses like turn around points and air flow don't really help me much. I've been roasting off the sound bites so far, Steve, as well as what I've learned here.

That said, I've set up my Artisan software to breakdown the 3 phases a little differently than most. I use your 20-25% for the first phase to 212* and the last DTR phase. I roast a lot of naturals and I don't want to heat too quickly. I try and center the modified ramp in between both 20-25% targets.

On my roaster I need to apply low heat for the first minute and a half and then try to increase only once based on density of the bean and charge amount. I can make little tweaks along the way, but I'd prefer if the laws of thermodynamics guide the declining RoR like an autopilot.

Here's a roast I did last night of some Panama Elida Natural. At 20% DTR it is fully developed and very fruit forward with a creamy mouth feel. Your guidelines work well for me.

I'm a proud and happy 90%er! Thanks for all you've done and do.

Thank you Scott for replying to this thread.
As your book (commandments etc.) have been a big issue of discussion, it's great that you've clarified this part. I personally roast mostly for drop coffee and I'm fond of lightly roasted coffees (even though every coffee have its own "perfect" spot). Most of the time I do find it difficult to achieve that 20-25% development time with e.g a City roast.
Anyhow, you've been a great inspiration to me with your book. While I may not follow your commandments to the letter, they are very well motivated (in your book) and they have become second nature to me. I.e a roast doesn't "look good" without a a constantly falling RoR etc.







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Scott Rao is interviewed on this week's Cat & Cloud podcast. He covers the Development Time Ratio and much more. Here's a Overcast.fm link: https://overcast.fm/+E8H335QyM